1. Field of the Invention
The present Invention relates to a slider assembly for a flying magnetic head and to a process of manufacturing the slider assembly.
2. Description of the Related Art
A typical magnetic head slider assembly has at least one magnetic read/write transducer at its rear end and produces a flying force to float itself above a rotating magnetic disk surface moving at high speed by means of pressurization of air flowing between its air bearing surface (ABS) and the magnetic disk surface.
Attempts have been made to try to adjust the flying height of the slider assembly to an appropriate value by balancing a spring force applied to the slider assembly with the flying force. However, when the slider assembly Is mounted to one end of a support arm which Is driven to swing around its fulcrum positioned at the other end, the flying height will be varied depending upon a radius position of the slider on the rotating disk. This variation in the flying height is caused by angular skew of the slider and by difference of an access velocity of the slider against the rotating disk.
FIG. 1 shows a measured characteristics of such flying height variation, in which the abscissas indicates an access velocity and a skew angle of the slider assembly and the ordinate indicates a flying height of the slider assembly. In the figure, a reference numeral 10 denotes a curve identified by flying height variation characteristics as a function of changes in the access velocity difference, curve 11 denotes a flying height variation as a function of the skew angle, and curve 12 denotes a practical flying height variation characteristics as a function of the composite characteristics of the flying height variations 10 and 11.
A slider head assembly having at least one air bearing surface provided with a specific transverse pressurization contour (TPC) along each side edge of the air bearing surface, so that its flying height is essentially insensitive to skew angle and to access velocity, is described in U.S. Pat. Nos. 4,673,996 and 4,870,519.
FIG. 2 shows a transversal cross sectional view of one fall of the slider head assembly described in the above-mentioned patents. In the figure, a reference numeral 20 denotes a fall extending rearwardly from a front edge of a slider assembly 21 and being projected from one surface of the slider 21 to form an air bearing surface 20a. Elements 22 and 23 denote notched recesses (TPC) formed along both side edges of the air bearing surface 20a of the rail 20, respectively. One of these notched recesses 22 and 23 serves for pressurization and the other serves for expansion of the rail 20 so as to compensate for the above-mentioned change of the flying height due to slider skew angle and/or access velocity. In order to perform this TPC function, the notched recesses 22 and 23 should have a very small depth of about 0.6 to 1.2 .mu.m, and the surface roughness of the recesses 22 and 23 have to be kept within .+-.0.15 .mu.m.
If such the notched recesses for compensating for a flying height change are milled by an ion milling method, the surface of the recesses may be formed extremely rough so that the depth of one part of the recesses may differ from that of the remaining part. Especially, when the ion beam is applied to the surface an angle which is at or near the perpendicular, the above-mentioned tendency of roughness will be extremely increased. FIGS. 3a and 3b show measured depths of the notched recesses 22 and 23 milled by means of an ion beam applied to the surface at an angle of nearly perpendicular according to the conventional technique, respectively.
If the surface of the recesses is formed rough and therefore the surface roughness is not kept within an effective range of .+-.0.15 .mu.m, a turbulent air flow will occur at these surfaces to produce a negative force. Thus, a transverse pressurization function caused by these notched recesses will not be obtained.
In case that an incident angle of the ion beam is inclined from zero degree (perpendicular with respect to the air bearing surface), the notched recesses will be formed with a small surface roughness but its stepping side wall will be milled in a tapered shape. If the stepping side wall is formed in a tapered shape, an effective transverse pressurization force cannot be expected.